Protective fuse having an auxiliary electrode



June 14, 1966 A. c. s'ruMPE ETAL. 3,256,447

PROTECTIVE FUSE HAVING AN AUXILIARY ELECTRODE Filed July 5,' 1965 5 Tusa 3 Figi f Fig F i g.4

5L I l l l i 5/ j d?? 4 Pag@ 6 5o 5 3 Jnvenm Hugust Crstan Stampe.

Kmws Traeger Httovnws vs claims. (clear-sas) y The present invention relates generally to the protective circuit art, and, more particularly, to a circuit arrangement for protecting semiconductor rectifiers, hereinafter referred to as diodes.

The use of highly 4sensitive electrical appliances and components in technical fields often requires that precautions be taken to protect .the circuitry against circuit overloads. r Semiconductor elements in particular are sensitive to such overloads because of the small thermal capacity ot the semiconductor material, and therefore such` elements' need protective circuitry which responds very quickly. Various known types of protective elements and protective circuits are not sufficiently rapid or are otherwise unsatisfactory for use with semiconductor elements arranged singly or in groups.

The main object of the present invention is to provide a fuse circuitv which utilizes advantages of known protective elements and circuitry while eliminating their disadvantages.

Another object of the invention is to provide a circuit of the type described which operates quickly to prevent current towto semiconductor devices, andwhich is simple and inexpensive in construction.

These objects and others ancillary thereto are accomplished according to preferred embodiments of the invention wherein a fuse element for protecting sensitive electrical components, ,like semiconductor elements, is constructed with one or more lfuse conductors. The fuse element is provided with at least three electrodes and the fuse conductor Vor conductors are connected between two such electrodes. The other auxiliary electrode or electrodes are disposed at a distance whic-h is spaced from the fuse conductor but adjacent thereto so that in normal operation there is no' direct galvanc connection between the auxiliary electrodes and the fuse conductor. When the fuse conductor'melts and an arc is created, one or several of the vauxiliary electrodes forms a base yfor the arc and thus the current path is transferred from the one electrode connected with'the fuse conductor to the auxiliary electrode or electrodes.

The semiconductor diode or a'group of semiconductor diodes is connected to the fuse device in such a manner that the lfuse conductor is connected in series with the semiconductor vdiode or group of semiconductor diodes to be protected, and the auxiliary electrode is connected with the contact terminal` of the semiconductor diode or the group thereof which faces away from the fuse conductor. Additional objects and advantages of lthe present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a circuit diagram of a protective circuit arrangement according to the present invention for protecting a single semiconductor diode.

FIGURE Ilia Circuit diagram of another embodi ment of the present invention wherein a group of semiconductor diodes forming a bridge circuit is protected. FIGURE 3 is a circuit diagram wherein more than one 'fuse device is used in the' protective circuit.

' FIGURE 4 is a circuit diagram illustrating a connection or polyphase systems.

FIGURE 5 is a circuit diagram of an arrangement using an additional fuse between the fuse terminal and the auxiliary electrode. l

Withmore particular reference now to FIGURE 1, a circuit incorporating a fuse element 5 is disclosed and this circuit `also includes a load 4, a semiconductor diode 3, all of which are connected in series with a power sup ply transformer 1. The inductance 6 is representative of the inductanees of the circuit. The fuse element 5 has two electrodes or terminals 51 and 53 with a fuse conductor 52 connected therebetween. An auxiliary electrode 54 is arranged spaced from but adjacent to the fuse conductor in such a manner that when the Vfuse conductor "52 responds and fuses because of excess or overload current, the arc which is thereby created, and with the arc the short circuit current also, are commutated to the auxiliary electrode which acts as a base for the arc. The fuse element 5 is connected into the circuit with its three contact terminals in such manner that the fuse conductor 52 connecting the terminals 51 and 53, is connected in series with a semiconductor diode 3, which is to be pro tected. A group of such semiconductor diodes to be protected could also be connected to the fuse element 5. The auxiliary electrode 54 has its contact terminal connected with the contact terminal of the semiconductor diode 3 which faces away from the fuse conductor.

A further feature of the invention isillustrated in FIG- URE 2 wherein similar elements as used in FIGURE l are given identical reference numerals. in this circuit the fuse element is used to protect a group o scmicon ductor diodes 3l, 32, 33, and 34, which-are arranged in the form of a bridge circuit 3. In this embodiment the fuse element 5 protects the semiconductor diodes of the bridge circuit against a short circuit on the direct current side. The fuse conductor 52 of fuse element 5 is connected to one alternating current side of the bridge 'while the auxiliary electrode 54 is connected with the other alternating current side of the diode bridge and these connections are accomplished by means of connection lines. When a short circuit occurs the fuse conductor 52 responds oy fusing or melting and an arc is pro duced which is commutated onto the auxiliary electrode 54. Because of commutation of the arc and thus of the short circuit current to the auxiliary electrode 54, the diode bridge and the short circuit are separated from the supply current or from .the mains. The current which is still effective because of the energy stored' hy the in ductance 6 of the circuit may continue to how via the arc between the electrode Sl' and the auxiliary electrode 54 without endangering the semiconductor diodes.

Another embodiment illustrated in particular `inl FIG- UR!E 3 shows a circuit arnangement which is to be used if a large inductance, indicated at 7 in the drawing, is present in the D.C. circuit of the diode arrangement. In .this event a fuse element 5' with a `fuse conductor 52 and auxiliary electrode 54' may be connected in addi- `tion to the fuse element in the alternating current connection line of the diode bridge as shown in FIGURE 3, or

` fit may be connected by itself into the D.C. circuit. In the event that there is a short circuit of the load 4, the energy which is stored by the induotanoe 7 before the fuse conductor 52' fuses, can be discharged through the auxiliary electrode 5-4 of the fuse element 5' without endangering the semiconductor diodes. i

A further embodiment of the invention is illustrated lin FIGURE 4, wherein a three-phase current bridge cir-k s., azstst't; ce Patented June 14 1966;* i

further advantageous arrangement is illustrated wherein a -further fuse element 50 is used for cutting olf the arc which occurs azterthe fuse conductor 52 in the fuse element has responded. This further fuse elernont is connectedon the sideof the energy source in series with the conductor 52. This additional fuse element may, for example, be a comm-'on melting fuse.

it wiil he understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of theappended claims.

What is claimed is:

1. A protective circuit for protecting semiconductor diodes, comprising, in combination: a fuse element having 4a fuse conductor connected between two termin-als, and an auxiliary electrode spaced from but adjacent to said 'fuse conductor; and semiconductor diode means to be protected connected in series with said fuse conductor, said auxiliary electrode being connected to provide a shunt discharge path across said semiconductor diode means when said fuse conductor melts.

2. A circuit as declined in claim 1 wherein said diode means includes a plurality of semiconductor diodes.

3. A circuit as dened in claim 2 wherein the semiconductor diodes are arranged to define a diode bridge circuit having two direct current terminals and two allternating current terminals.

4. A circuit as defined in claim 3 wherein the fuse conductor of said f-use element is connected to one alternating current terminal of the diode bridge and the auxiliary electrode is connected with the other alternating current terminal of the semiconductor diode bridge.

5. A circuit as defined in cla-im 3 wherein the fuse conductor of the fuse element is connected in ser-ies with one direct current terminal of the semiconductor diode bridge, and the auxiliary electrodeis connected with the other direct current terminal of the bridge.

6. A circuit as defined in claim l-wherein a further #fuse ele-ment is connected in series with the fuse conductor of said fuse element and the auxiliary electrode.

7. A circuit as defined in claim 4, comprising another I fuse element similar to said rsbmentioned fuse clement and having a fuse conductor connected in series wit-n one direct current termin-al of the diode bridgeand an auxiliary electrode connected with the other direct cun rent terminal.

8. A protective circuit for protecting semiconductor diodes, comprising, in combination:

-a plurality of fuse elements each having a fuse conductor connected between two .terminals and an auxiliary electrode spaced from but adjacent to the corresponding fuse conductor; and

a multipli-ase diode circuit to be protected, including a plurality of semiconductor diodes, said circuit including an alternating current connection line for cach phase and a diode in each line, there being as many yfuss elements as there are lines, one fuse element being connected to n respective line, 4and the auxiliary electrodes being connected with the neutral point of the current supply.

ReferencesvCited by the Examiner UNiTED STATES PATENTS 2,305,394 12/1942 Smith 20G-115 11/1949 Wallace et al. 200-115 X 

1. A PROTECTIVE CIRCUIT FOR PROTECTING SEMICONDUCTOR DIODES, COMPRISING, IN COMBINATION: A FUSE ELEMENT HAVING A FUSE CONDUCTOR CONNECTED BETWEEN TWO TERMINALS, AND AN AUXILIARY ELECTRODE SPACED FROM BUT ADJACENT TO SAID FUST CONDUCTOR; AND SEMICONDUCTOR DIODE MEANS TO BE PROTECTED CONNECTED IN SERIES WITH SAID FUSE CONDUCTOR, SAID AUXILIARY ELECTRODE BEING CONNECTED TO PROVIDE A SHUNT DISCHARGE PATH ACROSS SAID SEMICONDUCTOR DIODE MEANS WHEN SAID FUSE CONDUCTOR MELTS. 